The present invention generally pertains to electronic communications, and is particularly directed to an improved receiver and method for locating a source of RF radiation received by a four-arm spiral antenna.
A prior art receiver system for locating a source of RF radiation received by a four-arm spiral antenna is shown in FIG. 1. The system includes an RF mode matrix 10 coupled to the four-spiral arms of the antenna 11 for providing a first mode signal .SIGMA. on line 12 and a second mode signal .DELTA. on line 13. The first and second mode signals respectively represent sum and difference antenna patterns. The difference between the first and second mode signals is a function of the frequency of the received RF radiation. Therefore, an RF phase rotation compensation network 15 is provided to process the first and second mode signals to provide phase corrected first and second mode signals .SIGMA.' and .DELTA.' on lines 16 and 17 respectively. An attenuation network 19 may be provided to attenuate the phase corrected first and second mode signals on lines 16 and 17, depending upon system requirements. It may be necessary to attenuate the .SIGMA.' and .DELTA.' signals to minimize boresight errors. Attenuated phase corrected first and second mode signals k.SIGMA.' and k.DELTA.' are provided on lines 21 and 22 respectively to a receiver 23. The k.SIGMA.' and k.DELTA.' signals are processed by the receiver 23 to provide output signals .epsilon..sub.x and .epsilon..sub.y on lines 25 and 26. The .epsilon..sub.x and .epsilon..sub.y signals are a function of the angular displacement of the radiation source in an angular measurement frame that is normal to the antenna axis; and are useful for locating the RF radiation source, such as by tracking, guidance and/or direction finding.
The RF mode matrix 10 and the RF phase compensation network 15 substantially add to the cost, packaging size and complexity of the monopulse receiver system.